The present invention relates in part to an open-end spinning rotor having a fiber-collecting groove, which rotor comprises two rotor parts connected to one another, and to a process for producing such a rotor as herewith disclosed.
Open-end spinning rotors are conventionally made in one piece. However, for various reasons, it is also known to produce multi-part open-end spinning rotors. It is possible in this way to produce even complicated rotor shapes more simply and more economically than by forming one-piece open-end spinning rotors.
To permit a spinning rotor to be cleaned pneumatically, it may be divided, for example, in the region of a fiber-collecting groove (Swiss Patent Specification No. 458,216 and German Offenlegungsschrift No. 2,103,171). The two rotor parts can be removed from one another so that fibers and yarn remains can be sucked off radially between the two rotor parts.
Because of the play necessary to ensure requisite movability, there is a danger that fibers and dirt constituents will be jammed between the movable parts. There is also the danger that the interacting surfaces of the fiber-collecting groove will in time be affected by movements and constituents possibly jammed inside to the detriment of perfect yarn formation.
Apart from the fact that the production of multi-part spinning rotors can enable break-down cleaning of the spinning rotors, the production of multi-part spinning rotors of this type is usually to avoid the necessity of having to turn spinning rotors on a lathe from a solid body (as in German Offenlegungsschrift No. 2,058,340). Another object may be to manufacture simple parts when the open-end spinning rotor itself may have a relatively complex shape to generate the necessary operating vacuum (as in German Offenlegungsschrift No. 2,058,340 and German Auslegeschrift 2,159,248).
In such a case, a sliding wall and a fiber-collecting groove are provided in a first rotor part, and a fan is provided on another rotor part. The two rotor parts are then connected to one another via connecting bolts or directly by means of a press fit.
It has also been proposed to produce multi-part spinning rotors, with one rotor part specially designed according to necessary spinning properties, while the other rotor part is designed to meet required strength properties. In such instances, the two rotor parts are connected to one another by means of an engagement or adhesive connection or by means of a shrink-on sleeve (as in German Patent Specification Nos. 2,939,325 and 2,939,326).
In both of the foregoing cases, the parting gap between the two individual parts constituting the spinning rotor is not located in the region of the collecting groove since any loosening of this connection between these individual parts results in an irregular fiber-collecting groove and consequently also in uneven yarn.
All these various attempts have nevertheless failed, since they cannot be put into effect economically or in a practical way in industrial production. Open-end spinning rotors produced in such ways either are incapable of spinning or do not withstand the high speeds required.
One object of the present invention is to provide a method of producing in a simple and economical way a serviceable open-end spinning rotor which is capable of spinning and which comprises several rotor parts.
According to this invention, this and other objects may be achieved with a parting gap between the rotor parts which opens into a fiber-collecting groove, and is formed at least partially as a weld seam. Before being connected, the separate rotor parts are produced and machined completely independently of one another. Since the parting gap opens into the fiber-collecting groove, the groove is easily accessible before connection. This ensures a high degree of universality and flexibility in the production of open-end spinning rotors and even enables the formation of extreme forms of the fiber-collecting groove, e.g., undercut, unusually deep or very acute-angled fiber-collecting grooves.
The joining of the two rotor parts by means of a weld seam guarantees a secure wear-resistant connection between the two rotor parts. At the same time, and if appropriate for a given situation, the rotor parts may be held against one another under prestress. Such a connection between two rotor parts is thereby reliably prevented from working loose, thus also excluding the possibility that fibers and dirt will be jammed in the parting gap.
In principle, the parting gap can assume a wide variety of forms, e.g., cylinder or cone shell, but a parting gap opening radially into the weld seam is particuarly advantageous in terms of production and also for most intended uses.
According to one preferred embodiment of this invention, each of the two rotor parts has a flange, and the parting gap is located between these flanges. As a result, the spinning rotor can be formed with very thin walls so as to achieve as low a power consumption (i.e., power input requirement for rotation) as possible. This is because the flanges ensure that the spininng rotor has good dynamic (rotational) stability even at high speeds.
In another preferred embodiment of this invention, the wall thickness of the flange for the rotor part which constitutes the rotor bottom is formed greater than the wall thickness of the rotor part which accomodates a sliding wall. At the same time, the flange with the thicker cross-section not only fulfills the purpose of ensuring that the spinning rotor has dynamic stability even at high rotational speeds, but permits the milling off of material at that point for balancing, without weakening the cross-section of the actual spinning rotor and thereby reducing its dynamic stability.
The connection between the two rotor parts by means of a weld seam also guarantees, long term, that the parting gap will remain sufficiently narrow that no fibers and no dirt can become stuck there. To press the two rotor parts against one another with particular firmness during connection, the parting gap is appropriately limited by surfaces of the flanges which are non-parallel relative to one another in the unconnected state. In the connected state, the edges of the flanges facing the fiber-collecting groove are held against one another under prestress by means of the weld seam.
To obtain a shaped fiber-collecting groove in a simple way without any cutting, the fiber-collecting groove is preferably formed as an angular annular slot which is produced as a result of stamping of at least one of the two rotor parts. As a result of this stamping, the stamped surface is compressed and its wearing resistance consequently increased, without the surface structure being changed thereby.
Alternatively, in order to increase the wearing resistance of the fiber-collecting groove even further, at least part of the groove may be formed by an insert ring which is clamped adjoining the sliding wall and between the two rotor parts so as to limit the parting gap radially inwards. The advantage of such an insert ring is that it may comprise a material chosen independently of the material which comprises the remaining spinning rotor. To ensure a high wearing resistance, the insert ring preferably comprises a ceramic material.
Annular insert rings forming at least part of one fiber-collecting groove are to an extent known (German Utility Models Nos. 7,622,639 and 7,622,656). With such spinning rotors, the insert ring must extend up to the open end of the spinning rotor, with the result that the weight of the spinning rotor becomes very great. It therefore also consumes a large amount of energy during its operation.
In contrast, the present invention makes it possible to restrict the insert ring solely to the region of the fiber-collecting groove. The insert ring in this invention then may comprise a material, for example ceramic, differing from that of the remaining region of the fiber-collecting surface, and especially differing from the sliding wall of the spinning rotor.
The insert ring of this invention can perform differing functions and may therefore also take on differing forms accordingly. If it is desired for the insert ring to only perform the function of guaranteeing the depth of the fiber-collecting groove over a long term, then the two rotor parts may be advantageously provided with coaxial annular slots aligned with one another for accomodating the insert ring.
An insert ring forming at least part of the fiber-collecting groove is preferably profiled on its inner periphery. In this way, the insert ring comprises not only the bottom of the fiber-collecting groove, but also its side walls, thus increasing the dynamic stability of the fiber-collecting groove and consequently the spinning properties of the rotor over a long period of time.
So that the fiber-collecting groove may be given any desired form when an insert ring is used, in a further embodiment of this invention the insert ring may comprise a two part ring with the respective parts against one another in the region of their largest inside diameter.
The open-end spinning rotor is preferably made from sheet metal by means of plastic shaping. In such a case, the insert ring may likewise comprise profiled sheet metal which is held against the rotor parts under prestress by means of the rotor parts connected to one another.
In accordance with one aspect of this invention, to produce an open-end spinning rotor of this type, the two rotor parts are connected to one another by means of welding, the rotor parts being arranged relative to the welding location and rotated past the latter such that the weld seam forms on the outside of the open-end spinning rotor and does not project into the fiber-collecting groove. A fiber-collecting groove of any desired form can thereby be produced in a simple way, without its form being adversely affected when the rotor parts are joined together. Consequently, there are also no disadvantageous effects on the fibers during spinning.
The two rotor parts may be advantageously pressed against one another during the welding operation.
Particularly light-weight open-end spinning rotors can be obtained, in accordance with the invention, if at least the rotor part accomodating the sliding wall for the fibers is produced by means of non-cutting shaping, with the fiber-collecting groove acquiring its shape as a result of stamping.
To increase the strength of the fiber-collecting groove, in a further aspect of the process according to this invention, the two rotor parts receive in the region where subsequently their fiber-collecting groove will be formed recesses into which (when the two rotor parts are joined together) is inserted an insert ring. The ring is secured in this position as a result of the welding of the two rotor parts to one another.
By producing rotors in accordance with this invention, the above-described disadvantages of the prior art are avoided. Furthermore, an open-end spinning rotor according to this invention can be produced in a simple way and by simple means. Because of the many possible modifications of a rotor's fiber-collecting surface within the scope of this invention, the rotor can be used universally. Even the most extreme forms of a rotor can be produced without difficulty and without time-consuming measures. Moreover, the open-end spinning rotor is dynamically (dimensionally) stable and wear-resistant while at the same time possessing a low power consumption characteristic.